Heartburn pathophysiology
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Heartburn Pathophysiology: Key Mechanisms and Distinctions
Acid Reflux and Esophageal Mucosal Damage
Heartburn is most commonly associated with gastroesophageal reflux disease (GERD), where stomach acid flows back into the esophagus, causing irritation and the classic burning sensation. In GERD, acid exposure can damage the esophageal lining, leading to visible erosions (erosive esophagitis) or microscopic changes such as dilated intercellular spaces in nonerosive reflux disease (NERD) Orlando2008Barlow2005. This acid-mediated injury is a primary driver of heartburn symptoms in GERD and NERD Miwa2016Orlando2008Barlow2005.
Functional Heartburn and Visceral Hypersensitivity
Not all heartburn is caused by acid reflux. Functional heartburn (FH) is characterized by heartburn symptoms without evidence of abnormal acid exposure or esophageal injury. The main mechanism in FH is believed to be visceral hypersensitivity, where the esophagus becomes overly sensitive to normal stimuli, including minor acid exposure or even non-acidic events Miwa2016Frazzoni2004Barlow2005+2 MORE. This hypersensitivity can be due to changes in nerve function or central processing of pain signals Miwa2016Hirsch2024Patel2020.
Immunological and Tissue Resistance Factors
Recent research highlights the role of immunological mechanisms in the esophageal mucosa, which may contribute to both mucosal damage and symptom generation in heartburn. In addition, impaired tissue resistance—where the esophageal lining is less able to withstand normal reflux—can also play a role, especially in NERD and some cases of FH Miwa2016Orlando2008Barlow2005.
Esophageal Motility and Functional Disorders
Esophageal motility disorders, such as abnormal lower esophageal sphincter (LES) function, can contribute to heartburn by allowing more frequent or prolonged reflux episodes. However, in functional heartburn, motility is typically normal, and symptoms are not linked to reflux events Tamura2015Riegler2005Patel2020. Proper diagnostic testing, including manometry and pH monitoring, is essential to distinguish between reflux-related and functional causes Tamura2015Riegler2005Patel2020.
Overlap with Other Functional Gastrointestinal Disorders
Functional heartburn often overlaps with other functional gastrointestinal disorders, such as irritable bowel syndrome (IBS). This overlap suggests shared underlying mechanisms, including heightened sensitivity and psychological factors like anxiety . Patients with FH are more likely to have IBS and anxiety compared to those with reflux-related heartburn .
Clinical Implications and Treatment Approaches
The distinction between GERD, NERD, and FH is important because treatment strategies differ. Acid-suppressing medications are effective for GERD and NERD but less so for FH, where neuromodulators and psychological interventions may be more beneficial Miwa2016Hirsch2024Patel2020. New therapies targeting immunological pathways and visceral hypersensitivity are being explored Miwa2016Hirsch2024.
Conclusion
Heartburn arises from a combination of acid reflux, esophageal mucosal damage, visceral hypersensitivity, and, in some cases, immunological changes. GERD and NERD are primarily acid-mediated, while functional heartburn is driven by hypersensitivity and often overlaps with other functional disorders. Accurate diagnosis using endoscopy, pH monitoring, and manometry is crucial for effective management and tailored treatment.
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Most relevant research papers on this topic
‘Functional heartburn’: symptom for achalasia or hypertensive lower oesophageal sphincter?
Functional heartburn may be a symptom of functional disorders like achalasia or hypertensive lower esophageal sphincter, and exclusion of these disorders is crucial for accurate definition of functional heartburn patients.
Functional Heartburn and Chest Pain: A Review of Esophageal Neuromodulation
Neuromodulation therapy is often necessary for treating functional heartburn and chest pain, as it helps understand the underlying pathophysiology and provides effective treatment options.
Functional Heartburn Overlaps With Irritable Bowel Syndrome More Often than GERD
Functional heartburn (FH) is more frequently associated with irritable bowel syndrome (IBS) than GERD and hypersensitive esophagus (HE), suggesting common pathways and treatment options.
Untangling Non-erosive Reflux Disease From Functional Heartburn.
Non-erosive reflux disease (NERD) and functional heartburn are common causes of refractory heartburn, and diagnosis requires endoscopy and reflux testing.
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